DESCRIPTION: The temporomandibular disorders (TMDs) are a complex group of conditions involving masticatory muscles and/or temporomandibular joints and characterized by chronic facial pain. The etiology and pathogenesis of TMDs are multifactorial, including a strong association with depression and the occurrence of environmental stressors, with a strong predominance of women with these disorders (75-84%). It is known that dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, the main stress hormone axis, occurs in both depression and stress-related disorders. Recent evidence also demonstrates HPA dysregulation in other conditions related to TMDs: in particular, in fibromyalgia. This is a condition of generalized myalgia with a great deal of clinical overlap with masticatory muscle disorders (MMDs), a major sub-group of TMDs. Fibromyalgia also shows a similar high female predominance and is associated with high rates of depression and stress. Furthermore, there is evidence of important gender differences in HPA axis function resulting in an increased stress responsiveness and susceptibility to HPA dysregulation in women, thus providing an explanation for the high female predominance of fibromyalgia, depression and MMD. This study will examine the comorbidity of MMD and disorders associated with HPA stress axis dysregulation including fibromyalgia and stress-related psychiatric disorders, including depression, and test the hypothesis that women with MMD have an underlying HPA axis abnormality similar to that which occurs in fibromyalgia, namely HPA axis hypofunction, which is the underlying pathophysiological basis of both disorders. HPA function will be studied in women with MMD, (with and without comorbid fibromyalgia and depression) compared to normal controls, in terms of circadian and pulsatile patterns of basal cortisol secretion, using an intensive 24-hour plasma cortisol sampling paradigm. Women will be studied during both follicular and luteal phases of the menstrual cycle to test the hypothesis that there will be menstrual cycle-phase related fluctuations in symptoms and HPA axis function. These multidisciplinary studies will provide an understanding of the pathophysiological basis of the relationship of MMD to seemingly disparate conditions such as fibromyalgia and depressive disorders, as well as the higher prevalence in women, leading to a more rational basis for diagnosis and treatment of MMD.